i get alot of users on a regular basis calling the helpdesk because thay cannot sign into Lync. The users were able to sign in the previous day and nothing was changed on their systems. the error they get is "cannot sign in to Lync cannot sign in because the server version is incompatible" (screenshot below) but the user has the correct version. here is the interesting part... if i go in and delete their SIP profile folder and ask them to sign back in, it works and they are back on.
does anyone know why this is happening? it can happen to the same user many times or it can be a random user for the first time.